Methods and challenges of a dementia prevalence study
NZSA2024
Claudia Rivera-Rodriguez, PhD
Found that the sampling/doorknocking strategy was reasonable
We were able to train up multi-ethnic interviewers
Response rate at the door-knocking stage was 75% but at subsequent stages was about 25%
Demonstrated that a prevalence study was feasible in Māori, Chinese, Indian and Pākehā, not in Pacific populations.
# Load the DiagrammeR package
library(DiagrammeR)
# Create the flow diagram with rounded corners for the boxes
# Load the DiagrammeR package
library(DiagrammeR)
# Create the flow diagram with rounded corners, custom fill colors, and horizontal layout
graph <- "
digraph flow {
# Set graph layout to horizontal (left to right)
rankdir = LR;
# Define node properties with rounded corners and fill colors
node [shape = rect, style = filled, fontname = Helvetica, fontsize = 12, width = 2, height = 0.6, color = black, fontcolor = black, style = rounded];
# Define the nodes (phases) with custom fill colors
Areas [label = 'Phase 1: Areas', fillcolor = lightgreen, width = 2.5]
Meshblocks [label = 'Phase 2: Meshblocks', fillcolor = lightblue, width = 2.5]
Screening [label = 'Phase 3: Participants', fillcolor = lightcoral, width = 2.5]
# Define the edges (arrows) with labels and colors
Areas -> Meshblocks [label = '', fontsize = 10, color = blue, fontcolor = blue];
Meshblocks -> Screening [label = '', fontsize = 10, color = green, fontcolor = green];
# Styling the edges (arrows)
edge [arrowhead = vee, arrowsize = 1.5, color = gray];
}
"
#grViz(graph)
# Render the diagram with horizontal layoutApart from the phases, our desing had three main features:
Phase 1: Areas
Stratification by district (AKL or CHC) & rural/urban
Sample size allocation: 75% for AKL and 25% for CHC
30%+ Chinese or 20%+ Indian all have a high chance of selection (60%+)
Phase 2: Meshblocks
Proportion of Meshblock selcted form each area
Denser Chinese/Indian meshblocks have higher chances of selection
Phase 3: Participants
Screening tool for dementia- everyone Positive selected, 50% negative selected
Only 30% pakeha selected
We decided on a margin of error of about 0.03,
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